ACCESSIBILITY LAYERS:

Semantic HTML Foundation:
├── <button> for buttons (not <div>)
├── <nav> for navigation regions
├── <form> and <fieldset> for forms
├── <a> for links
└── Heading hierarchy (h1-h6)

ARIA Enhancement:
├── Landmark roles (navigation, main, complementary)
├── State attributes (aria-expanded, aria-current)
├── Relationship attributes (aria-labelledby, aria-describedby)
└── Live regions (aria-live, role="alert")

Visual Accessibility:
├── Color contrast (4.5:1 minimum)
├── Focus indicators (focus-visible:ring-2)
├── Motion reduction (prefers-reduced-motion)
└── Text scaling support

Keyboard Accessibility:
├── Tab order management
├── Focus trapping in modals
├── Escape key handling
└── Arrow key navigation (where appropriate)

// Navigation with accessible label
<nav role="navigation" aria-label="pagination">
  <ul>
    <li><a href="/page/1">1</a></li>
    <li><a href="/page/2" aria-current="page">2</a></li>
  </ul>
</nav>

// Breadcrumb navigation
<nav aria-label="breadcrumb">
  <ol>
    <li><a href="/">Home</a></li>
    <li aria-current="page">Products</li>
  </ol>
</nav>

// Main content area
<main role="main" id="main-content">
  {/* Page content */}
</main>

// Accordion/Collapsible
<button
  aria-expanded={isOpen}
  aria-controls={`content-${id}`}
  onClick={() => setIsOpen(!isOpen)}
>
  Section Title
</button>
<div
  id={`content-${id}`}
  aria-hidden={!isOpen}
  hidden={!isOpen}
>
  {/* Collapsible content */}
</div>

// Tabs
<div role="tablist" aria-label="Settings tabs">
  <button
    role="tab"
    aria-selected={activeTab === 'general'}
    aria-controls="panel-general"
    tabIndex={activeTab === 'general' ? 0 : -1}
  >
    General
  </button>
</div>
<div
  role="tabpanel"
  id="panel-general"
  aria-labelledby="tab-general"
  hidden={activeTab !== 'general'}
>
  {/* Tab content */}
</div>

// Menu/Dropdown
<button
  aria-haspopup="menu"
  aria-expanded={isOpen}
  aria-controls="menu-items"
>
  Options
</button>
<div
  id="menu-items"
  role="menu"
  aria-hidden={!isOpen}
>
  <button role="menuitem">Edit</button>
  <button role="menuitem">Delete</button>
</div>

// core/components/ui/form.tsx pattern
<FormItem>
  <FormLabel htmlFor={formItemId}>
    Email
  </FormLabel>
  <FormControl>
    <Input
      id={formItemId}
      aria-describedby={
        !error
          ? formDescriptionId
          : `${formDescriptionId} ${formMessageId}`
      }
      aria-invalid={!!error}
      aria-required={required}
    />
  </FormControl>
  <FormDescription id={formDescriptionId}>
    We'll never share your email.
  </FormDescription>
  {error && (
    <FormMessage id={formMessageId} role="alert">
      {error.message}
    </FormMessage>
  )}
</FormItem>

// Status announcements (polite)
<div aria-live="polite" aria-atomic="true" className="sr-only">
  {statusMessage}
</div>

// Error alerts (assertive)
<div role="alert" className="text-destructive">
  {errorMessage}
</div>

// Toast notifications
<div
  role="status"
  aria-live="polite"
  aria-atomic="true"
>
  {notification}
</div>

// Button focus pattern
<button
  className="focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 focus-visible:ring-offset-background"
>
  Click me
</button>

// Input focus pattern
<input
  className="focus-visible:outline-none focus-visible:ring-1 focus-visible:ring-ring"
/>

// Custom focus indicator
<div
  tabIndex={0}
  className="focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2"
  onKeyDown={(e) => {
    if (e.key === 'Enter' || e.key === ' ') {
      e.preventDefault()
      handleAction()
    }
  }}
>
  Interactive element
</div>

// Logical tab order (follows DOM)
<header>
  <nav tabIndex={0}>...</nav>  {/* First */}
</header>
<main tabIndex={0}>...</main>  {/* Second */}
<aside tabIndex={0}>...</aside> {/* Third */}

// Remove from tab order
<div tabIndex={-1}>
  {/* Programmatically focusable but not in tab order */}
</div>

// Skip link pattern
<a
  href="#main-content"
  className="sr-only focus:not-sr-only focus:absolute focus:top-4 focus:left-4 focus:z-50 focus:bg-background focus:px-4 focus:py-2"
>
  Skip to main content
</a>

// core/components/ui/dialog.tsx
import * as DialogPrimitive from '@radix-ui/react-dialog'

// Radix Dialog automatically:
// - Traps focus within modal
// - Returns focus on close
// - Handles Escape key
// - Manages aria-hidden on background

<DialogPrimitive.Root>
  <DialogPrimitive.Trigger>Open</DialogPrimitive.Trigger>
  <DialogPrimitive.Portal>
    <DialogPrimitive.Overlay />
    <DialogPrimitive.Content>
      {/* Focus is trapped here */}
      <DialogPrimitive.Close>
        <span className="sr-only">Close</span>
        <X aria-hidden="true" />
      </DialogPrimitive.Close>
    </DialogPrimitive.Content>
  </DialogPrimitive.Portal>
</DialogPrimitive.Root>

// Visually hidden but announced by screen readers
<span className="sr-only">Close dialog</span>

// Icon button with accessible name
<Button variant="ghost" size="icon">
  <X aria-hidden="true" />
  <span className="sr-only">Close</span>
</Button>

// More pages indicator
<span aria-hidden="true">...</span>
<span className="sr-only">More pages</span>

// Hide decorative icons from screen readers
<ChevronRight aria-hidden="true" className="h-4 w-4" />

// Separator in breadcrumb
<span role="presentation" aria-hidden="true">/</span>

// Loading spinner
<Loader2
  aria-hidden="true"
  className="h-4 w-4 animate-spin"
/>
<span className="sr-only">Loading...</span>

// 1. Visible text (preferred)
<button>Delete Item</button>

// 2. aria-label for icon-only buttons
<button aria-label="Delete item">
  <TrashIcon aria-hidden="true" />
</button>

// 3. aria-labelledby for complex labels
<div id="dialog-title">Confirm Deletion</div>
<div aria-labelledby="dialog-title">
  {/* Content described by title */}
</div>

// 4. Form labels
<Label htmlFor="email">Email address</Label>
<Input id="email" type="email" />

/* contents/themes/default/styles/globals.css */
:root {
  /* High contrast pairs */
  --primary: oklch(0.2050 0 0);           /* Dark */
  --primary-foreground: oklch(0.9850 0 0); /* Light - 4.5:1+ contrast */

  --destructive: oklch(0.5770 0.2450 27.3250);
  --destructive-foreground: oklch(1 0 0);

  /* Focus ring with sufficient contrast */
  --ring: oklch(0.7080 0 0);
}

.dark {
  /* Inverted for dark mode */
  --primary: oklch(0.9220 0 0);
  --primary-foreground: oklch(0.2050 0 0);
}

// ✅ CORRECT - Use semantic tokens that guarantee contrast
<p className="text-foreground">Primary text</p>
<p className="text-muted-foreground">Secondary text</p>
<button className="bg-primary text-primary-foreground">
  Action
</button>

// ❌ WRONG - Arbitrary colors may not have proper contrast
<p className="text-gray-400">Low contrast text</p>
<button className="bg-blue-300 text-blue-100">
  Poor contrast
</button>

// core/components/ui/double-range.tsx
<div
  ref={thumbMinRef}
  role="slider"
  aria-label="Minimum value"
  aria-valuemin={min}
  aria-valuemax={max}
  aria-valuenow={localValue[0]}
  tabIndex={disabled ? -1 : 0}
  className="focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring"
  onKeyDown={handleKeyDown}  // Arrow keys to adjust
/>

// core/components/ui/pagination.tsx
<nav role="navigation" aria-label="pagination">
  <PaginationPrevious aria-label="Go to previous page" />

  {pages.map((page) => (
    <PaginationLink
      aria-current={page === current ? 'page' : undefined}
    >
      {page}
    </PaginationLink>
  ))}

  <PaginationNext aria-label="Go to next page" />
</nav>

// core/components/ui/alert.tsx
<div
  ref={ref}
  role="alert"
  className={cn(alertVariants({ variant }), className)}
  {...props}
/>

import { axe, toHaveNoViolations } from 'jest-axe'

expect.extend(toHaveNoViolations)

test('should have no accessibility violations', async () => {
  const { container } = render(<MyComponent />)
  const results = await axe(container)
  expect(results).toHaveNoViolations()
})

// ❌ NEVER: Div as button
<div onClick={handleClick}>Click me</div>

// ✅ CORRECT: Use semantic button
<button onClick={handleClick}>Click me</button>

// ❌ NEVER: Icon-only button without accessible name
<button><TrashIcon /></button>

// ✅ CORRECT: Add aria-label or sr-only text
<button aria-label="Delete item">
  <TrashIcon aria-hidden="true" />
</button>

// ❌ NEVER: Remove focus indicator completely
<button className="outline-none focus:outline-none">
  No focus indicator
</button>

// ✅ CORRECT: Custom focus indicator
<button className="focus-visible:ring-2 focus-visible:ring-ring">
  Visible focus
</button>

// ❌ NEVER: Low contrast text
<p className="text-gray-300 bg-white">Hard to read</p>

// ✅ CORRECT: Use semantic tokens
<p className="text-muted-foreground bg-background">Readable</p>

// ❌ NEVER: Missing form labels
<input type="email" placeholder="Email" />

// ✅ CORRECT: Proper label association
<Label htmlFor="email">Email</Label>
<input id="email" type="email" />

// ❌ NEVER: Images without alt text
<img src="/logo.png" />

// ✅ CORRECT: Descriptive alt or empty for decorative
<img src="/logo.png" alt="Company Logo" />
<img src="/decorative.png" alt="" aria-hidden="true" />

// ❌ NEVER: Auto-playing media without controls
<video autoPlay src="/video.mp4" />

// ✅ CORRECT: User controls and captions
<video controls>
  <source src="/video.mp4" />
  <track kind="captions" src="/captions.vtt" />
</video>